Exhaust gas control apparatus of an internal combustion engine

Abstract

A first cylinder and a second cylinder are provided. A first exhaust pipe is connected to the first cylinder and a second exhaust pipe is connected to the second cylinder. A communicating pipe connects together an intermediate portion of the first exhaust pipe with an intermediate portion of the second exhaust pipe. An exhaust gas control catalyst is arranged in the second exhaust pipe downstream of the portion to which the communicating pipe is connected. Exhaust gas amount reducing devices are provided which reduce the amount of exhaust gas that flows from the first exhaust pipe into the second exhaust pipe through the communicating pipe during execution of rich/lean burn control which performs combustion with an air-fuel ratio of an air-fuel mixture that is richer than the stoichiometric air-fuel ratio in one of the first cylinder and second cylinder and performs combustion with an air-fuel ratio of an air-fuel mixture that is leaner than the stoichiometric air-fuel ratio in the other cylinder.

1. An exhaust gas control apparatus of an internal combustion engine having a first cylinder and a second cylinder, comprising:
 a first exhaust pipe connected to the first cylinder; 
 a second exhaust pipe connected to the second cylinder; 
 a communicating pipe that connects together an intermediate portion of the first exhaust pipe and an intermediate portion of the second exhaust pipe; 
 an exhaust gas control catalyst arranged in the second exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected; and 
 an exhaust gas amount reducing device which reduces an amount of exhaust gas that flows from the first exhaust pipe into the second exhaust pipe through the communicating pipe during execution of a rich/lean burn control which performs combustion with an air-fuel ratio of an air-fuel mixture that is richer than the stoichiometric air-fuel ratio in one of the first cylinder and second cylinder, and performs combustion with an air-fuel ratio of an air-fuel mixture that is leaner than the stoichiometric air-fuel ratio in the other cylinder. 
 
   
   
     2. The exhaust gas control apparatus of an internal combustion engine according to  claim 1 , wherein the exhaust gas amount reducing device reduces the amount of exhaust gas that flows from the first exhaust pipe into the second exhaust pipe through the communicating pipe when a temperature of the exhaust gas control catalyst is higher than a predetermined temperature. 
   
   
     3. The exhaust gas control apparatus of an internal combustion engine according to  claim 1 , wherein the exhaust gas amount reducing device reduces the amount of exhaust gas that flows from the first exhaust pipe into the second exhaust pipe through the communicating pipe by increasing a pressure in the second exhaust pipe upstream of the exhaust gas control catalyst. 
   
   
     4. The exhaust gas control apparatus of an internal combustion engine according to  claim 3 , further comprising;
 an exhaust gas control valve which changes a flow path area of the second exhaust pipe and is arranged in the second exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein the exhaust gas amount reducing device increases the pressure in the second exhaust pipe upstream of the exhaust gas control catalyst by reducing the flow path area of the second exhaust pipe using the exhaust gas control valve. 
 
   
   
     5. The exhaust gas control apparatus of an internal combustion engine according to  claim 1 , wherein the exhaust gas amount reducing device reduces the amount of exhaust gas that flows from the first exhaust pipe into the second exhaust pipe through the communicating pipe by decreasing the pressure in the first exhaust pipe upstream of the intermediate portion to which the communicating pipe is connected. 
   
   
     6. The exhaust gas control apparatus of an internal combustion engine according to  claim 5 , further comprising:
 an exhaust gas control valve which changes the flow path area of the first exhaust pipe and is arranged in the first exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein the exhaust gas amount reducing device decreases the pressure in the first exhaust pipe upstream of the intermediate portion to which the communicating pipe is connected by increasing the flow path area of the first exhaust pipe using the exhaust gas control valve. 
 
   
   
     7. The exhaust gas control apparatus of an internal combustion engine according to  claim 1 , further comprising:
 an exhaust turbine of a turbocharger, which is arranged in the first exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected. 
 
   
   
     8. The exhaust gas control apparatus of an internal combustion engine according to  claim 5 , further comprising:
 an exhaust turbine of a turbocharger, which is arranged in the first exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein the exhaust gas amount reducing device decreases the pressure in the first exhaust pipe upstream of the intermediate portion to which the communicating pipe is connected by increasing an opening amount of a wastegate valve of the turbocharger. 
 
   
   
     9. The exhaust gas control apparatus of an internal combustion engine according to  claim 1 , further comprising:
 a communication control valve which changes a flow path area of the communicating pipe and is arranged in the communicating pipe, wherein the exhaust gas amount reducing device reduces the amount of exhaust gas that flows from the first exhaust pipe into the second exhaust pipe through the communicating pipe by reducing the flow path area of the communicating pipe using the communication control valve. 
 
   
   
     10. The exhaust gas control apparatus of an internal combustion engine according to  claim 1 , further comprising:
 a single common exhaust pipe that is connected to a downstream end of the first exhaust pipe and a downstream end of the second exhaust pipe; and 
 an exhaust gas control catalyst which is separate from the exhaust gas control catalyst and arranged in the common exhaust pipe, 
 wherein the rich/lean burn control is executed so as to supply exhaust gas of a rich air-fuel ratio and exhaust gas of a lean air-fuel ratio to the exhaust gas control catalyst arranged in the common exhaust pipe. 
 
   
   
     11. The exhaust gas control apparatus of an internal combustion engine according to  claim 1 , further comprising:
 an exhaust gas control catalyst arranged in the first exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected. 
 
   
   
     12. An exhaust gas control apparatus of an internal combustion engine having a first cylinder and a second cylinder, comprising:
 a first exhaust pipe connected to the first cylinder; 
 a second exhaust pipe connected to the second cylinder; 
 a communicating pipe that connects together an intermediate portion of the first exhaust pipe and an intermediate portion of the second exhaust pipe; 
 a single common exhaust pipe which is connected to a downstream end of the first exhaust pipe and a downstream end of the second exhaust pipe; 
 an exhaust gas control catalyst arranged in the common exhaust pipe; 
 an exhaust turbine of a turbocharger, which is arranged in the first exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected; and 
 an exhaust gas amount control apparatus which executes an exhaust gas control that controls i) an amount of exhaust gas that flows through the first exhaust pipe and into the exhaust gas control catalyst from the downstream end of the first exhaust pipe and ii) the amount of exhaust gas that flows through the second exhaust pipe and into the exhaust gas control catalyst from the downstream end of the second exhaust pipe such that a temperature of the exhaust gas control catalyst becomes equal to or close to a target temperature. 
 
   
   
     13. The exhaust gas control apparatus of an internal combustion engine according to  claim 12 , wherein the exhaust gas amount control apparatus controls i) the amount of exhaust gas that flows through the first exhaust pipe and into the exhaust gas control catalyst from the downstream end of the first exhaust pipe and ii) the amount of exhaust gas that flows through the second exhaust pipe and into the exhaust gas control catalyst from the downstream end of the second exhaust pipe by controlling a pressure in the first exhaust pipe. 
   
   
     14. The exhaust gas control apparatus of an internal combustion engine according to  claim 13 , further comprising:
 an exhaust gas control valve which changes a flow path area of the first exhaust pipe and is arranged in the first exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein the exhaust gas amount control apparatus controls the pressure in the first exhaust pipe by controlling an opening amount of the exhaust gas control valve. 
 
   
   
     15. The exhaust gas control apparatus of an internal combustion engine according to  claim 13 , wherein the turbocharger includes a wastegate valve, and the exhaust gas amount control apparatus controls the pressure in the first exhaust pipe by controlling the opening amount of the wastegate valve. 
   
   
     16. The exhaust gas control apparatus of an internal combustion engine according to  claim 12 , wherein the exhaust gas amount control apparatus controls i) the amount of exhaust gas that flows through the first exhaust pipe and into the exhaust gas control catalyst from the downstream end of the first exhaust pipe and ii) the amount of exhaust gas that flows through the second exhaust pipe and into the exhaust gas control catalyst from the downstream end of the second exhaust pipe by controlling the pressure in the second exhaust pipe. 
   
   
     17. The exhaust gas control apparatus of an internal combustion engine according to  claim 16 , further comprising:
 an exhaust gas control valve which changes the flow path area of the second exhaust pipe and is arranged in the second exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein the exhaust gas amount control apparatus controls the pressure in the second exhaust pipe by controlling the opening amount of the exhaust gas control valve. 
 
   
   
     18. The exhaust gas control apparatus of an internal combustion engine according to  claim 12 , wherein the exhaust gas amount control apparatus increases the amount of exhaust gas that flows through the first exhaust pipe and into the exhaust gas control catalyst from the downstream end of the first exhaust pipe when a temperature of the exhaust gas control catalyst is higher than a target temperature, and increases the amount of the exhaust gas that flows through the second exhaust pipe and into the exhaust gas control catalyst from the downstream end of the second exhaust pipe when the temperature of the exhaust gas control catalyst is lower than the target temperature. 
   
   
     19. The exhaust gas control apparatus of an internal combustion engine according to  claim 12 , wherein the exhaust gas amount control apparatus controls, in accordance with a load of the internal combustion engine during execution of the exhaust gas amount control, the amount of exhaust gas that flows through the first exhaust pipe and into the exhaust gas control catalyst from the downstream end of the first exhaust pipe such that the amount of exhaust gas that passes through the exhaust turbine of the turbocharger becomes equal to or close to a target amount. 
   
   
     20. An exhaust gas control apparatus of an internal combustion engine having a first cylinder and a second cylinder, comprising:
 a first exhaust pipe connected to the first cylinder; 
 a second exhaust pipe connected to the second cylinder; 
 a communicating pipe that connects together an intermediate portion of the first exhaust pipe and an intermediate portion of the second exhaust pipe; 
 a single common exhaust pipe which is connected to a downstream end of the first exhaust pipe and a downstream end of the second exhaust pipe; 
 an exhaust gas control catalyst arranged in the common exhaust pipe; 
 an exhaust turbine of a turbocharger, which is arranged in the first exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein a rich/lean burn control is executed which performs combustion with an air-fuel ratio of an air-fuel mixture that is richer than the stoichiometric air-fuel ratio in one of the first cylinder and second cylinder, and performs combustion with an air-fuel ratio of an air-fuel mixture that is leaner than the stoichiometric air-fuel ratio in the other cylinder, and exhaust gas of a rich air-fuel ratio and exhaust gas of a lean air-fuel ratio are supplied to the exhaust gas control catalyst in order to raise the temperature of the exhaust gas control catalyst when the exhaust gas control catalyst is in a predetermined state; and 
 an exhaust gas amount control apparatus which executes an exhaust gas amount control that increases the amount of exhaust gas that flows through the second exhaust pipe and into the exhaust gas control catalyst from the downstream end of the second exhaust pipe before the rich/lean burn control is executed. 
 
   
   
     21. The exhaust gas control apparatus of an internal combustion engine according to  claim 20 , wherein the exhaust gas amount control apparatus increases the amount of exhaust gas that flows through the second exhaust pipe and into the exhaust gas control catalyst from the downstream end of the second exhaust pipe by decreasing the pressure in the second exhaust pipe. 
   
   
     22. The exhaust gas control apparatus of an internal combustion engine according to  claim 21 , further comprising:
 an exhaust gas control valve which changes a flow path area of the second exhaust pipe and is arranged in the second exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein the exhaust gas amount control apparatus decreases the pressure in the second exhaust pipe by increasing an opening amount of the exhaust gas control valve. 
 
   
   
     23. The exhaust gas control apparatus of an internal combustion engine according to  claim 20 , wherein the exhaust gas amount control apparatus increases the amount of exhaust gas that flows through the second exhaust pipe and into the exhaust gas control catalyst from the downstream end of the second exhaust pipe by increasing the pressure in the first exhaust pipe. 
   
   
     24. The exhaust gas control apparatus of an internal combustion engine according to  claim 23 , further comprising:
 an exhaust gas control valve which changes the flow path area of the first exhaust pipe and is arranged in the first exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein the exhaust gas amount control apparatus increases the pressure in the first exhaust pipe by reducing the opening amount of the exhaust gas control valve. 
 
   
   
     25. The exhaust gas control apparatus of an internal combustion engine according to  claim 23 , wherein the turbocharger includes a wastegate valve and the exhaust gas amount control apparatus increases the pressure in the first exhaust pipe by reducing an opening amount of the wastegate valve. 
   
   
     26. The exhaust gas control apparatus of an internal combustion engine according to  claim 20 , wherein combustion in which the air-fuel ratio of the air-fuel mixture is the stoichiometric air-fuel ratio is performed in the second cylinder when the exhaust gas amount control apparatus is executing the exhaust gas amount control. 
   
   
     27. The exhaust gas control apparatus of an internal combustion engine according to  claim 26 , wherein combustion in which the air-fuel ratio of the air-fuel mixture is the stoichiometric air-fuel ratio is performed in the first cylinder when the exhaust gas amount control apparatus is executing the exhaust gas amount control. 
   
   
     28. An exhaust gas control apparatus of an internal combustion engine having a first cylinder and a second cylinder, comprising:
 a first exhaust pipe connected to the first cylinder; 
 a second exhaust pipe connected to the second cylinder; 
 a communicating pipe that connects together an intermediate portion of the first exhaust pipe and an intermediate portion of the second exhaust pipe; 
 a single common exhaust pipe which is connected to a downstream end of the first exhaust pipe and a downstream end of the second exhaust pipe; 
 an exhaust gas control catalyst arranged in the common exhaust pipe; 
 an exhaust turbine of a turbocharger, which is arranged in the first exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein a rich/lean burn control is executed which performs combustion with an air-fuel ratio of an air-fuel mixture that is richer than the stoichiometric air-fuel ratio in one of the first cylinder and second cylinder, and performs combustion with an air-fuel ratio of an air-fuel mixture that is leaner than the stoichiometric air-fuel ratio in the other cylinder, and exhaust gas of a rich air-fuel ratio and exhaust gas of a lean air-fuel ratio are supplied to the exhaust gas control catalyst in order to raise the temperature of the exhaust gas control catalyst when the exhaust gas control catalyst is in a predetermined state; and 
 an exhaust gas amount control apparatus which executes an exhaust gas amount control that increases the amount of exhaust gas that flows through the first exhaust pipe and into the exhaust gas control catalyst from the downstream end of the first exhaust pipe when the rich/lean burn control has ended. 
 
   
   
     29. The exhaust gas control apparatus of an internal combustion engine according to  claim 28 , wherein the exhaust gas amount control apparatus increases the amount of exhaust gas that flows through the first exhaust pipe and into the exhaust gas control catalyst from the downstream end of the first exhaust pipe by decreasing the pressure in the first exhaust pipe. 
   
   
     30. The exhaust gas control apparatus of an internal combustion engine according to  claim 29 , further comprising:
 an exhaust gas control valve which changes a flow path area of the first exhaust pipe and is arranged in the first exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein the exhaust gas amount control apparatus decreases the pressure in the first exhaust pipe by increasing an opening amount of the exhaust gas control valve. 
 
   
   
     31. The exhaust gas control apparatus of an internal combustion engine according to  claim 29 , wherein the turbocharger includes a wastegate valve and the exhaust gas amount control apparatus decreases the pressure in the first exhaust pipe by increasing the opening amount of the wastegate valve. 
   
   
     32. The exhaust gas control apparatus of an internal combustion engine according to  claim 28 , wherein the exhaust gas amount control apparatus increases the amount of exhaust gas that flows through the first exhaust pipe and into the exhaust gas control catalyst from the downstream end of the first exhaust pipe by increasing the pressure in the second exhaust pipe. 
   
   
     33. The exhaust gas control apparatus of an internal combustion engine according to  claim 31 , further comprising:
 an exhaust gas control valve which changes the flow path area of the second exhaust pipe and is arranged in the second exhaust pipe downstream of the intermediate portion to which the communicating pipe is connected, wherein the exhaust gas amount control apparatus increases the pressure in the second exhaust pipe by reducing the opening amount of the exhaust gas control valve.